Fan Dipole Troubles -Fail?

This is definitely a learn by doing hobby! If there’s one thing I learned this past week, it’s that not all antennas are going to work out the way you want them to! Especially multi-band antennas. Maybe I shouldn’t call my project a fail, maybe a lesson learned? I finally completed the Fan Dipole after my FlexWeave wire from The Wireman arrived promptly at my doorstep. I cut all of the lengths to the actual dipole length, not accounting for the length of the copper strip inside of the fan dipole, I wanted to leave the extra for headroom during pruning. So up ‘the beast’ went, I separated the elements best I could, already this thing was starting to look like an eye sore… what was I thinking? It looked a bit neater on the ‘Fence Fan-Dipole’ project over on eHam because his elements were all neatly strung to a fence underneath, but I didn’t have that kind of support underneath & I wanted to keep the elements as far apart from one another as I could.

So I hooked up the analyzer, and the closest to an acceptable SWR that I could immediately find was on 20 meters, at about ‘1.6’. Everything else was way off frequency and SWRs were unacceptable on all but 20. I started with the lowest frequency first, slowly nipping away a couple inches at a time, and rechecking everything, but I was noticing that the resonant frequency wasn’t really changing much as I was nipping away… ok… so what’s going on here… is the antenna possibly seeing a different set of legs as 40? So I looked further up and down the graph on 40m on the analyzer, nope, there was nothing even close. So I nipped a little more away, and kept checking, but I still couldn’t get it to resonate even close to where it should be on 40, it was closer to like 6.900 MHzSo I switched over to the 30m legs just to see if I could get the resonant frequency to change there, well I think it did a little bit, I wasn’t exactly writing everything down like I should have (lesson learned), or taken screen shots which I could have also of done.

I messed around with the legs a bit, trying to get them as high as I could, and I even moved them into different locations, spreading further apart, and sometimes closer together to try everything possible. I came to the possible conclusion that perhaps it was how I had the copper tape inside the PVC that was causing these issues. All of my connections were tight and snug, but after an entire day of trying to get this thing to work… I gave up. I was unable to get it to resonate on 40/30/17/15. The only band I was ok with was 20m which eventually showed a flat swr right near 14.100. I heard that these things were a pain to tune, but had no clue it would be this troublesome! I’m sure if I was able to get the antenna up much higher and had more free space it might be a bit easier, but I like to tune them where they will be deployed.

I’m still stumped. I put my OCF back up for now. It will stay up. That was way too many wires for my liking. Maybe I should have went with a ‘parrallel’ fan dipole and kept all of the elements together like the Alpha Delta fan dipoles are made, I may still try that in due time. I was a bit frustrated to say the least, putting all of that effort, time & money into an antenna that doesn’t work very well. So I decided to treat my OCF a bit and get it up higher & stealth it a bit more! Felt like such a crime to paint this beautiful balun from Balun Designs, but I think it turned out pretty sweet! I like using the high heat grill paint from the big box stores, it dries super quick, leaves a nice matte finish, and is very durable.

Did a quick check on the analyzer, and sure enough, the readings were just about right where they were before, still a little high on 80 (3:1) though. Acceptable for my liking.

A big thank you to F1PWS, IK2WJT, F5TIL, DG7NFX, & LY2VM for the DX this morning! 17 meters was booming into the Central United States while Europe was in their grey line for the evening. Gotta take advantage of those conditions! (still lets me know my antenna is working! :P)

Would changing to a 1:1 balun possibly make any difference on your SWR readings? You are looking at a 200 to 50 ohm impedance difference with a 4:1 balun.Each resonant antenna and the coaxial feedline should be closer to a 50 ohm impedance,which could be the reason for the high SWR values.

Johnny

1 December 2016 at
11:15 AM

Its a 1:1 current balun Dennis from DXEngineering. I’ve used it on monoband dipoles, just never a fan. My OCF is a 4:1 current balun, maybe I confused readers by including the two in the article! I’ve still got the fan… just waiting for Winter Field Day to take it out and test in an easier location and with some help!